Numerous neurobehavioral models have been proposed to account for the clinical manifestations of autism. Our research examining neuropsychologic function across domains modalities has provided evidence of concurrent impairments in higher order abilities across domains, intact simpler abilities in these same domains, and the integrity of basic information acquisition abilities. Based on the dissociation between simple and complex abilities within domains and the predominance of clinical impairments in domains with the highest demands for complex information processing, we have proposed that autism is the consequence of a selective impairment in complex information processing that spares simpler information processing in the same domains, and does not involve the visual-spatial domain. The goals of this project are: 1) to define the impaired and intact abilities within and across domains that characterize neuropsychologic functioning in autism and ot define the qualitative features of the deficits that are specific to autism and independent of the influence of mental retardation on the expression of these deficits; 2) to address key unanswered questions about the neutropsychologic characteristics of the deficits and intact abilities in autism and provide evidence that several alternative explanations proposed for this pattern are not supported; and 3) to determine the specific strategies or methods used by subjects for task performance. Thje goals of Project I will be accomplished through the administration of: 1) a battery of neuropsychologic tests that assess a range of abilities within and across domains and in both the autitory and visual modalities (Component 1); 2) selected neuropsychologic procedures that further characterize deficits and intact abilities, address key unresolved questions about their nature, and investigate alternative deficits proposed to explain the deficit pattern in autism (Component 2); and 3) experimental cognitive procedures that provide a detailed cognitive analysis of executive, analytic, and pattern analysis abilities used in task performance (Component 3). The neuropyschologic procedures from Component 1 will serve a broader purpose of providing a common linkfor studies in Projects II and III to the clinical expression of the deficits and to the broader pattern of deficits in autism.